Update the phosphor drag-drop mime

src/filebrowser/listing.ts

@@ -175,7 +175,7 @@ const IS_MAC = !!navigator.platform.match(/Mac/i);
 /**
  * The factory MIME type supported by phosphor dock panels.
  */
-const FACTORY_MIME = 'application/x-phosphor-widget-factory';
+const FACTORY_MIME = 'application/vnd.phosphor.widget-factory';
 
 
 /**

src/notebook/output-area/widget.ts

@@ -18,7 +18,7 @@ import {
 } from 'phosphor/lib/core/signaling';
 
 import {
-  Drag, DropAction
+  Drag
 } from 'phosphor/lib/dom/dragdrop';
 
 import {
@@ -54,7 +54,7 @@ const DRAG_THRESHOLD = 5;
 /**
  * The factory MIME type supported by phosphor dock panels.
  */
-const FACTORY_MIME = 'application/x-phosphor-widget-factory';
+const FACTORY_MIME = 'application/vnd.phosphor.widget-factory';
 
 /**
  * The class name added to an output area widget.